summary An anterior inferior iliac spine (AIIS) avulsion is an apophyseal avulsion injury seen in adolescent athletes as a result of eccentric contraction of the rectus femoris. Diagnosis is made with pelvis radiographs that shows an avulsion off the AIIS. Treatment is nonoperative with rest, icing, NSAIDs and activity modification. Epidemiology Demographics most often in adolescents between the ages 14-17 males more often than females occurs most often in sports involving kicking Etiology Pathophysiology mechanism typically occurs due to eccentric contraction of the rectus femoris (femoral n.) as hip extends and knee is flexed causes avulsion of its anatomic origin off the pelvis Anatomy Anterior inferior iliac spine a bony prominence just above acetabulum is the origin of the direct head of the rectus femoris (femoral n.) Presentation History sudden "pop" in pelvis Symptoms pain and weakness Physical exam antalgic gait anterior hip pain and hip flexion weakness Imaging Radiographs show avulsion of AIIS Treatment Nonoperative bed-rest, ice, activity modification indications almost all treated successfully nonoperatively technique hip flexed for 2 weeks position lessens stretch of affected muscle and apophysis follow with guarded weight bearing for 4 week Complications Loss of reduction Delayed union